An overview of a satellite network system, such as disclosed in the above-identified related application, is illustrated in FIG. 1. The satellite network system design provides the capability for METs and FESs to access one or more multiple beam satellites located in geostationary orbit to obtain communications services.
The heart of the satellite network system for each of the networks is the Network Control System (NCS) which monitors and controls each of the networks. The principal function of the NCS is to manage the overall satellite network system, to manage access to the satellite network system, to assign satellite circuits to meet the requirements of mobile customers and to provide network management and network administrative and call accounting functions.
The satellites each transmit and receive signals to and from METs at L-band frequencies and to and from Network Communications Controllers (NCCs) and Feederlink Earth Stations (FESS) at Ku-band frequencies. Communications at L-band frequencies is via a number of satellite beams which together cover the service area. The satellite beams are sufficiently strong to permit voice and data communications using inexpensive mobile terminals and will provide for frequency reuse of the L-band spectrum through inter-beam isolation. A single beam generally covers the service area.
The satellite network system provides the capability for mobile earth terminals to access one or more multiple beam satellites located in geostationary orbit for the purposes of providing mobile communications services. The satellite network system is desired to provide the following general categories of service.
Mobile Telephone Service (MTS) provides point-to-point circuit switched voice connections between mobile and public switched telephone network (PSTN) subscriber stations. Calls can be originated by either the mobile terminal or terrestrial user. Mobile terminal-to-mobile terminal calls are also supported.
Mobile Radio Service (MRS) provides point-to-point circuit switched connections between mobile terminal subscriber stations and subscriber stations in a private network (PN) which is not a part of the PSTN. Calls can be originated from either end. Mobile terminal-to-mobile terminal calls are also supported.
Mobile Telephone Cellular Roaming Service (MTCRS) provides Mobile Telephone Service to mobile subscribers who are also equipped with cellular radio telephones. When the mobile terminal is within range of the cellular system, calls are serviced by the cellular system. When the mobile terminal is not in range of the cellular system, the MTCRS is selected to handle the call and appears to the user to be a part of the cellular system. Calls can be originated either from the MET or the PSTN. Mobile terminal-to-mobile terminal calls are also supported.
NET Radio (NR) service provides point-to-multipoint circuit switched connections between mobile terminal subscriber stations and a central base station. Mobile users are able to listen to two-way conversations and to transmit using a push-to-talk mode of operation.
Mobile Data Service (MDS) provides a packet switched connection between a data terminal equipment (DTE) device at a mobile terminal and a data communications equipment (DCE)/DTE device connected to a public switched packet network. Integrated voice/data operation is also supported.
The satellites are designed to transmit signals at L-band frequencies in the frequency band 1530-1559 MHz. They will receive L-band frequencies in the frequency band 1631.5-1660.5 MHz. Polarization is right hand circular in both bands. The satellites will also transmit in the Ku frequency band, 10,750 MHz to 10,950 MHz, and receive Ku-band signals in the frequency band 13,000 to 13,250 MHz.
The satellite transponders are designed to translate communications signals accessing the satellite at Ku-band frequencies to an L-band frequency in a given beam and vice versa. The translation will be such that there is a one-to-one relation between frequency spectrum at Ku-band and frequency spectrum in any beam at L-band. The satellite transponders will be capable of supporting L-band communications in any portion of the 29 MHz allocation in any beam.
Transponder capacity is also provided for Ku-band uplink to Ku-band down-link for signalling and network management purposes between FESs and NCCs. The aggregate effective isotropic radiated power (AEIRP) is defined as that satellite e.i.r.p. that would result if the total available communications power of the communications subsystem was applied to the beam that covers that part of the service area. Some of the key performance parameters of the satellite are listed in FIG. 2.
The satellite network system interfaces to a number of entities which are required to access it for various purposes. FIG. 3 is a context diagram of the satellite network system illustrating these entities and their respective interfaces. Three major classes of entities are defined as user of communications services, external organizations requiring coordination, and network management system.
The users of satellite network communications services are MET users who access the satellite network system either via terrestrial networks (PSTN, PSDN, or Private Networks) or via METs for the purpose of using the services provided by the system. FES Owner/Operators are those organizations which own and control FESs that provide a terrestrial interface to the satellite network. When an FES becomes a part of the satellite network, it must meet specified technical performance criteria and interact with and accept real-time control from the NCCs. FES Owner/Operators determine the customized services that are offered and are ultimately responsible for the operation and maintenance of the FES. Customers and service providers interact with the Customer Management Information System within the Network Management System.
The satellite network system interfaces to, and performs transactions with, various operational units to implement its functions. Interaction with a Satellite Operations Center (SOC) enables the system to maintain cognizance of the availability of satellite resources (e.g. in the event of satellite health problems, eclipse operations, etc.) and, from time to time, to arrange for any necessary satellite reconfiguration to meet changes in traffic requirements.
A satellite network management system (NMS) is normally located at an administration's headquarters and may comprise three major functional entities: Customer Management Information System (CMIS), Network Engineering, and System Engineering (NE/SE). These entities perform functions necessary for the management and maintenance of the satellite network system that are closely tied to the way the administration intends to do business.
CMIS provides customers and service providers with assistance and information including problem resolution, service changes, and billing/usage data. Customers include individual MET owners and fleet managers of larger corporate customers. Service providers are the retailers and maintenance organizations that interact face to face with individual and corporate customers.
Network Engineering (NE) develops plans and performs analysis in support of the system. NE analyzes the requirements of the network. It reconciles expected traffic loads with the capability and availability of space and ground resources to produce frequency plans for the different beams within the system. Contingency plans are defined for failure situations. System Engineering (SE) engineers the subsystems, equipment and software that is needed to expand capacity to meet increases in traffic demands and to provide new features and services which become marketable to subscribers.
Necessary to the successful interaction of the various stations in the communications system is the appropriate interface between the satellites and the network. Delivery of messages must be coordinated. As the satellite network system interfaces with outside organizations that lease resources on satellite network, such resources must be allocated and managed in a manner suited to the users' needs. Still other outside users do not lease resources on satellite network satellites but require operational coordination.